WASHINGTON—President Donald Trump’s approach to trade is often counterproductive because he alienates rather than cultivates allies, uniting them against the U.S. instead of China.

In my column yesterday, I laid out an alternate history in which Mr. Trump forces China to fundamentally change its mercantilist expropriation of foreign companies’ technology and market share. This seems like a stretch given Mr. Trump’s track record to date. On the other hand, it’s a scenario that calls for strengths possessed by Mr. Trump that...